Petrified wood (from the Greek root "petro" meaning "rock" or "stone", literally "wood turned into stone") is a type of fossil, it consists of fossil wood where all the organic materials have been replaced with minerals (most often a silicate, such as quartz), while retaining the original structure of the wood.

What turned the wood to stone?Petrified wood has been preserved for millions of years by the process of petrification. This process turns the wood into quartz crystal, which is very brittle and shatters. Even though petrified wood is fragile, it is also harder than steel.Petrified wood is known for its exquisite color and detail. Some pieces of petrified wood have retained the original cellular structure of the wood; the grain can easily be seen. Petrified wood can be found throughout the desert regions. It is easy to find and identify. It is used often in jewelry making and for other types of decorative artwork.  

The process of petrification is not completely understood because researchers have not been able to duplicate the process in the laboratory, where it can be observed and measured. But, certain conditions that must have existed for petrification to
occur are known. Oxygen, which causes oxidation or rotting of all types of materials, would have to have been kept away from the dead plant material to prevent it from decaying before it was preserved. Most likely, the dead plant material was
deprived of oxygen by being buried by sediments settling in water covering the plants. Much of the fossil wood found today is a product of ancient river and flood plain environments.

After rapid burial, the tree reacts to percolating water. Three things may happen. The log may disintegrate and not be fossilized. The log may be reduced by compression to a coal or it may become petrified. If petrification takes place, minerals from percolating water are deposited in fluid-filled openings in the wood. This process is called permineralization and it preserves the tissues of the wood! In some situations minerals may also substitute for the woody tissues of the log. This process is called replacement. Most petrified woods are permineralized . The entire process is not fully understood but is being actively studied. The final condition, necessary for petrification, is time. The mineral replacement process is very slow, probably taking
millions of years.

It is not wood that makes petrified wood colorful, but the chemistry of the petrifying groundwater. Minerals such as manganese, iron, and copper were in the water/mud during the petrification process. These minerals give petrified wood a variety of color ranges. Quartz crystals are colorless, but when iron is added to the process the crystals become stained with a yellow or red tint.

Following is a list of minerals and related color hues: